///////////////////////////////////////////////////////////////////////////////
//
//                          IMPORTANT NOTICE
//
// The following open source license statement does not apply to any
// entity in the Exception List published by FMSoft.
//
// For more information, please visit:
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// https://www.fmsoft.cn/exception-list
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//////////////////////////////////////////////////////////////////////////////
/*
 *   This file is part of MiniGUI, a mature cross-platform windowing
 *   and Graphics User Interface (GUI) support system for embedded systems
 *   and smart IoT devices.
 *
 *   Copyright (C) 2002~2018, Beijing FMSoft Technologies Co., Ltd.
 *   Copyright (C) 1998~2002, WEI Yongming
 *
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *   Or,
 *
 *   As this program is a library, any link to this program must follow
 *   GNU General Public License version 3 (GPLv3). If you cannot accept
 *   GPLv3, you need to be licensed from FMSoft.
 *
 *   If you have got a commercial license of this program, please use it
 *   under the terms and conditions of the commercial license.
 *
 *   For more information about the commercial license, please refer to
 *   <http://www.minigui.com/blog/minigui-licensing-policy/>.
 */
/* Derived data constructed for each Huffman table */

#define HUFF_LOOKAHEAD    8    /* # of bits of lookahead */

typedef struct {
  /* Basic tables: (element [0] of each array is unused) */
  INT32 mincode[17];        /* smallest code of length k */
  INT32 maxcode[18];        /* largest code of length k (-1 if none) */
  /* (maxcode[17] is a sentinel to ensure jpeg_huff_decode terminates) */
  int valptr[17];        /* huffval[] index of 1st symbol of length k */

  /* Link to public Huffman table (needed only in jpeg_huff_decode) */
  JHUFF_TBL *pub;

  /* Lookahead tables: indexed by the next HUFF_LOOKAHEAD bits of
   * the input data stream.  If the next Huffman code is no more
   * than HUFF_LOOKAHEAD bits long, we can obtain its length and
   * the corresponding symbol directly from these tables.
   */
  int look_nbits[1<<HUFF_LOOKAHEAD]; /* # bits, or 0 if too long */
  UINT8 look_sym[1<<HUFF_LOOKAHEAD]; /* symbol, or unused */
} d_derived_tbl;

/* Expand a Huffman table definition into the derived format */
EXTERN(void) jpeg_make_d_derived_tbl JPP((j_decompress_ptr cinfo,
                JHUFF_TBL * htbl, d_derived_tbl ** pdtbl));


/*
 * Fetching the next N bits from the input stream is a time-critical operation
 * for the Huffman decoders.  We implement it with a combination of inline
 * macros and out-of-line subroutines.  Note that N (the number of bits
 * demanded at one time) never exceeds 15 for JPEG use.
 *
 * We read source bytes into get_buffer and dole out bits as needed.
 * If get_buffer already contains enough bits, they are fetched in-line
 * by the macros CHECK_BIT_BUFFER and GET_BITS.  When there aren't enough
 * bits, jpeg_fill_bit_buffer is called; it will attempt to fill get_buffer
 * as full as possible (not just to the number of bits needed; this
 * prefetching reduces the overhead cost of calling jpeg_fill_bit_buffer).
 * Note that jpeg_fill_bit_buffer may return FALSE to indicate suspension.
 * On TRUE return, jpeg_fill_bit_buffer guarantees that get_buffer contains
 * at least the requested number of bits --- dummy zeroes are inserted if
 * necessary.
 */

typedef INT32 bit_buf_type;    /* type of bit-extraction buffer */
#define BIT_BUF_SIZE  32    /* size of buffer in bits */

/* If long is > 32 bits on your machine, and shifting/masking longs is
 * reasonably fast, making bit_buf_type be long and setting BIT_BUF_SIZE
 * appropriately should be a win.  Unfortunately we can't do this with
 * something like  #define BIT_BUF_SIZE (sizeof(bit_buf_type)*8)
 * because not all machines measure sizeof in 8-bit bytes.
 */

typedef struct {        /* Bitreading state saved across MCUs */
  bit_buf_type get_buffer;    /* current bit-extraction buffer */
  int bits_left;        /* # of unused bits in it */
  boolean printed_eod;        /* flag to suppress multiple warning msgs */
} bitread_perm_state;

typedef struct {        /* Bitreading working state within an MCU */
  /* current data source state */
  const JOCTET * next_input_byte; /* => next byte to read from source */
  size_t bytes_in_buffer;    /* # of bytes remaining in source buffer */
  int unread_marker;        /* nonzero if we have hit a marker */
  /* bit input buffer --- note these values are kept in register variables,
   * not in this struct, inside the inner loops.
   */
  bit_buf_type get_buffer;    /* current bit-extraction buffer */
  int bits_left;        /* # of unused bits in it */
  /* pointers needed by jpeg_fill_bit_buffer */
  j_decompress_ptr cinfo;    /* back link to decompress master record */
  boolean * printed_eod_ptr;    /* => flag in permanent state */
} bitread_working_state;

/* Macros to declare and load/save bitread local variables. */
#define BITREAD_STATE_VARS  \
    register bit_buf_type get_buffer;  \
    register int bits_left;  \
    bitread_working_state br_state

#define BITREAD_LOAD_STATE(cinfop,permstate)  \
    br_state.cinfo = cinfop; \
    br_state.next_input_byte = cinfop->src->next_input_byte; \
    br_state.bytes_in_buffer = cinfop->src->bytes_in_buffer; \
    br_state.unread_marker = cinfop->unread_marker; \
    get_buffer = permstate.get_buffer; \
    bits_left = permstate.bits_left; \
    br_state.printed_eod_ptr = & permstate.printed_eod

#define BITREAD_SAVE_STATE(cinfop,permstate)  \
    cinfop->src->next_input_byte = br_state.next_input_byte; \
    cinfop->src->bytes_in_buffer = br_state.bytes_in_buffer; \
    cinfop->unread_marker = br_state.unread_marker; \
    permstate.get_buffer = get_buffer; \
    permstate.bits_left = bits_left

/*
 * These macros provide the in-line portion of bit fetching.
 * Use CHECK_BIT_BUFFER to ensure there are N bits in get_buffer
 * before using GET_BITS, PEEK_BITS, or DROP_BITS.
 * The variables get_buffer and bits_left are assumed to be locals,
 * but the state struct might not be (jpeg_huff_decode needs this).
 *    CHECK_BIT_BUFFER(state,n,action);
 *        Ensure there are N bits in get_buffer; if suspend, take action.
 *      val = GET_BITS(n);
 *        Fetch next N bits.
 *      val = PEEK_BITS(n);
 *        Fetch next N bits without removing them from the buffer.
 *    DROP_BITS(n);
 *        Discard next N bits.
 * The value N should be a simple variable, not an expression, because it
 * is evaluated multiple times.
 */

#define CHECK_BIT_BUFFER(state,nbits,action) \
    { if (bits_left < (nbits)) {  \
        if (! jpeg_fill_bit_buffer(&(state),get_buffer,bits_left,nbits))  \
          { action; }  \
        get_buffer = (state).get_buffer; bits_left = (state).bits_left; } }

#define GET_BITS(nbits) \
    (((int) (get_buffer >> (bits_left -= (nbits)))) & ((1<<(nbits))-1))

#define PEEK_BITS(nbits) \
    (((int) (get_buffer >> (bits_left -  (nbits)))) & ((1<<(nbits))-1))

#define DROP_BITS(nbits) \
    (bits_left -= (nbits))

/* Load up the bit buffer to a depth of at least nbits */
EXTERN(boolean) jpeg_fill_bit_buffer
    JPP((bitread_working_state * state, register bit_buf_type get_buffer,
         register int bits_left, int nbits));


/*
 * Code for extracting next Huffman-coded symbol from input bit stream.
 * Again, this is time-critical and we make the main paths be macros.
 *
 * We use a lookahead table to process codes of up to HUFF_LOOKAHEAD bits
 * without looping.  Usually, more than 95% of the Huffman codes will be 8
 * or fewer bits long.  The few overlength codes are handled with a loop,
 * which need not be inline code.
 *
 * Notes about the HUFF_DECODE macro:
 * 1. Near the end of the data segment, we may fail to get enough bits
 *    for a lookahead.  In that case, we do it the hard way.
 * 2. If the lookahead table contains no entry, the next code must be
 *    more than HUFF_LOOKAHEAD bits long.
 * 3. jpeg_huff_decode returns -1 if forced to suspend.
 */

#define HUFF_DECODE(result,state,htbl,failaction,slowlabel) \
{ register int nb, look; \
  if (bits_left < HUFF_LOOKAHEAD) { \
    if (! jpeg_fill_bit_buffer(&state,get_buffer,bits_left, 0)) {failaction;} \
    get_buffer = state.get_buffer; bits_left = state.bits_left; \
    if (bits_left < HUFF_LOOKAHEAD) { \
      nb = 1; goto slowlabel; \
    } \
  } \
  look = PEEK_BITS(HUFF_LOOKAHEAD); \
  if ((nb = htbl->look_nbits[look]) != 0) { \
    DROP_BITS(nb); \
    result = htbl->look_sym[look]; \
  } else { \
    nb = HUFF_LOOKAHEAD+1; \
slowlabel: \
    if ((result=jpeg_huff_decode(&state,get_buffer,bits_left,htbl,nb)) < 0) \
    { failaction; } \
    get_buffer = state.get_buffer; bits_left = state.bits_left; \
  } \
}

/* Out-of-line case for Huffman code fetching */
EXTERN(int) jpeg_huff_decode
    JPP((bitread_working_state * state, register bit_buf_type get_buffer,
         register int bits_left, d_derived_tbl * htbl, int min_bits));
